Hot water expansion tank

I need to install a hot water expansionn tank Sunday, and the only place can get on e is the Home depot or Lowes. Is there a difference in quality as compared to one I could get Monday morning from the plumbing supply shop?

Can't say. But, make sure you get one proper for your application - they come in hydronic heating versions (non-potable), and potable versions. THen, you have to determine what size you need which depends on the volume, temperature swings, and pressure of your supply.

Not really, but a potable water one will be galvanized and probably glass lined. A hydronic one will be black steel, which will rust out quickly in a fresh water system. Size, and initial pressure, are not as important as some make it out to be.

Size becomes more important in the wintertime when you exhaust the WH's volume. All that cold water will need more room to expand than a more normal usage, where only a small amount of cold water then needs to expand as it is heated. The tank's bladder gets stressed more if it gets stretched further than designed (to accommodate that extra volume of expanding water), thus, the pressure and volume should match your needs.